Psychometric validation of the revised Symptoms and Impacts Questionnaire for Crohn's Disease (SIQ-CD) and Ulcerative Colitis (SIQ-UC)
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Issue Date
2026
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Conference Proceedings
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Background: The Symptoms and Impacts Questionnaire for Crohn's Disease (SIQ-CD) and Ulcerative Colitis (SIQ-UC) are patient-reported outcome measures developed to support endpoint assessment in Crohn's disease (CD) and ulcerative colitis (UC) clinical trials.1 Based upon regulatory feedback, the SIQ-CD/UC were revised and are currently used in clinical studies such as the actiVE ulcerative colitis, a RanDomIsed Controlled Trial (VERDICT).2 Here we report results of a cross-sectional psychometric validation study of the new version of the SIQ-CD/UC. Method(s): Adult participants (>=18 years of age) with an established diagnosis of CD or UC were eligible. All participants had an initial clinical assessment, as well as a centrally-read endoscopy for those without an ostomy or perianal disease. Participants were divided into pre-specified subgroups based on disease extent and endoscopic severity in UC, and clinical scores in CD, to capture the full spectrum of disease activity. The study consisted of two parts. Part 1 aimed to finalise the content validity of the new version of the SIQ measures. Part 2, conducted in the USA, the UK, and Canada, performed psychometric evaluation of the SIQ scores, such that the SIQ-CD (35item, 11 domains) or SIQ-UC (33-item, 10 domains) was assessed for 7 consecutive days after inclusion. In Part 1, the completion of SIQ scoring was followed by an interview to evaluate the content validity of the score. In Part 2, approximately the first 40 participants included in each disease category completed the SIQ score for 14 days. Result(s): The cognitive debriefing interviews (Part 1) involved 18 participants with CD and 19 with UC (Table). The revised SIQ measures were well understood and conceptually relevant. The validation study (Part 2) involved 120 participants with CD (mean age 41 years; 56% male) and 120 participants with UC (mean age 43 years; 50% male) (Table). Test-retest reliability was assessed with 66/120 participants (SIQ-CD) and 77/120 (SIQ-UC), finding an interclass correlation coefficient >0.7 for all domains in both scores except for "Nausea and Vomiting" in SIQCD. Both scores also had a good relationship to disease severity (although not to disease extent in UC). Overall domain consistency was good in both scores (Cronbach's alpha >0.70), except for the "Nausea and Vomiting" domain (Cronbach's alpha =0.63). Inter-item correlations were generally <0.9, except for items related to fatigue in both scores, quality of life in UC, and abdominal pain in CD. Conclusion(s): Overall, these results show good psychometric properties of the revised SIQ-CD/UC and confirm the scale structure. Future studies are needed to evaluate responsiveness and meaningful change thresholds.
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Journal of Crohn's and Colitis
Volume
20